Method for forming nano sensing chip by selective deposition of sensing materials through device-localized Joule heating and nano sensing chip thereof

ABSTRACT

A method for forming a nanodevice sensing chip includes forming nanodevices having a sensing region capable of producing localized Joule heating. Individual nanodevice is electrical-biased in a chemical vapor deposition (CVD) system or an atomic layer deposition (ALD) system enabling the sensing region of the nanodevice produce localized Joule heating and depositing sensing material only on this sensing region. A sensing chip is formed via nanodevices with sensing region of each nanodevice deposited various materials separately. The sensing chip is also functioned under device Joule self-heating to interact and detect the specific molecules.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of copending application Ser. No.16/052,484, filed on Aug. 1, 2018, which claims priority under 35 U.S.C.§ 119(a) to application Ser. No. 10/711,510, filed in Taiwan on May 3,2018, all of which are hereby expressly incorporated by reference intothe present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to a method for forming a nanosensing chip. Particularly, the present invention relates to a methodfor forming a nano sensing chip by selective deposition of sensingmaterials through device-localized Joule heating and chemical vapordisposition (CVD) or atomic layer disposition (ALD) and a nano sensingchip thereof.

2. Description of the Prior Art

Because of their high sensitivity in response to changes in surfacepotential, nanodevices (e.g. nanowire (NW) field-effect transistors andnanobelt (NB) devices) have been developed for sensing applications.However, the nanodevices need specific modifications to exhibitsignificant selectivity toward target species.

Conventional surface modifications for nanodevices include: (1)evaporating or sputtering sensing materials through the shadow masktechniques, (2) physically or chemically adsorbing or bonding moleculeswith specific functional group onto the surface through theself-assembled monolayer (SAM) techniques, (3) utilizing localized Jouleheating to ablate a region of polymer film on the nanodevice andevaporating or sputtering sensing materials through the lift-offprocesses, (4) utilizing localized Joule heating to grow sensingmaterials in solutions, or (5) utilizing localized Joule heating toablate a region of the film on the nanodevice and forming a layer ofsensing materials through the SAM techniques.

However, shadow mask techniques, SAM processes, and lift-off processesare very difficult to modify selectively only at specific regions of thedevice surface, especially when the device is further scaled down. Asthe devices become smaller and smaller, it is difficult to selectivelyevaporate or sputter materials only on the device channel by usingshadow mask, so the chance of depositing materials outside the devicechannel is getting higher and higher, not feasible for low concentrationsensing applications. Moreover, when depositing different materials onindividual devices by the lift-off techniques, the processes of coating,ablating, lift-off, and evaporating or sputtering are repeated fordifferent materials, and the ablating or lift-off processes will causecontaminations or peeling of the previously deposited materials,decreasing the sensitivity of the nanodevices for sensing applicationsor even resulting in devices fail.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for forming a nanosensing chip by selective deposition of sensing materials on specificregions through localized Joule heating and the chemical vapordeposition (CVD) or the atomic layer deposition (ALD). The specificregion is the most sensitive region of the device channel in response tochanges in surface potential, so the method is suitable for manufactureof nanoscale sensing devices.

In an embodiment, the invention provides a method for forming a nanosensing chip. The method includes: forming a nanodevice having a regioncapable of producing localized Joule heating, and in a CVD system or anALD system enabling the region of the nanodevice produce localized Jouleheating and depositing a sensing material only on the region.

It is another object of the invention to provide a method for forming anano sensing chip by sequentially electrical-biasing the nanodevices toselectively depositing different sensing materials on the sensingregions of different nanodevices through localized Joule heating and CVDor ALD, so as to simplify the manufacturing processes and prevent thepreviously deposited sensing materials from contamination or peeling.

In another embodiment, the invention provides a method for forming anano sensing chip. The method includes: forming a plurality ofnanodevices into a first group and a second group, each of the firstgroup or the second group including at least one of the plurality ofnanodevices, each of the plurality of nanodevices having a sensingregion capable of producing localized Joule heating; in a CVD system oran ALD system enabling the sensing region of the at least one nanodevicein the first group produce localized Joule heating and depositing afirst sensing material only on the sensing region of the at least onenanodevice in the first group; and after the first sensing material isdeposited, enabling the sensing region of the at least one nanodevice inthe second group produce localized Joule heating and depositing a secondsensing material only on the sensing region of the at least onenanodevice in the second group, wherein the at least one nanodevice inthe second group is different from the at least one nanodevice in thefirst group, and the second sensing material is different from the firstsensing material.

It is yet another object of the invention to provide a nano sensingchip, which consists of multiple nanodevices with various sensingmaterials. Each of the nanodevices can function under device Jouleself-heating at appropriate working temperature. The nano structure(e.g. nanowire or nanobelt) Joule self-heating can effectively reducethe power consumption during sensing operation and can be applied tosensing applications of multiple gases in comparison to conventionalgas-sensing techniques requiring additional heat source and larger powerconsumption.

In another embodiment, a nano sensing chip of the invention includes aplurality of nanodevices divided into a first group and a second group,each of the first group and the second group including at least one ofthe plurality of nanodevices, each nanodevice including a source, adrain, and a device channel with two ends electrically connecting thesource and the drain, the device channel including a lightly-dopedregion; a first sensing material deposited on the lightly-doped regionsof the at least one nanodevice in the first group; and a second sensingmaterial deposited on the lightly-doped region of the at least onenanodevice in the second group, wherein the at least one nanodevice inthe second group is different from the at least one nanodevice in thefirst group, and the second sensing material is different from the firstsensing material.

Compared to the conventional techniques, the method of the inventionutilizes localized Joule-heating to selectively deposit sensingmaterials on specific regions through CVD or ALD, which is suitable formanufacturing nano sensing chips. Moreover, the method of the inventionfurther selectively deposits various sensing materials on the sensingregions of different nanodevices by sequentially electrical-biasing thenanodevices, so the manufacturing processes are simplified, andcontamination or peeling of the previously deposited sensing materialsis also prevented. Moreover, the nano sensing chip of the invention hasvarious sensing materials deposited on different nanodevices in a samechip, so the nano sensing chip of the invention is suitable sensingapplications of multiple gases and is able to function under deviceJoule self-heating, superior in portable gas sensing applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one color drawing.Copies of this patent or patent application publication with colordrawing will be provided by the USPTO upon request and payment of thenecessary fee.

FIG. 1A is a schematic view of an embodiment of nanodevices;

FIG. 1B is a schematic side view of an embodiment of selectivedeposition of sensing materials on nanodevices through localized Jouleheating in a CVD or ALD system;

FIG. 2 presents atomic force microscopy (AFM) and top-view scanningelectron microscopy (SEM) images after ALD (or CVD) for selectivedeposition of Pt and ZnO on the lightly-doped region of the nanodevicechannel for various numbers of deposition cycles, (a) 10 cycles, (b) 20cycles, and (c) 30 cycles;

FIG. 3 shows average thicknesses of Pt and ZnO after various numbers ofdeposition cycles;

FIG. 4 shows average coverage lengths of Pt and ZnO after variousnumbers of deposition cycles;

FIG. 5 presents AFM and SEM images after ALD (or CVD) for selectivedeposition of Pt and ZnO through a given number of deposition cycles onthe lightly-doped region of the nanodevice channel under various biasvoltages, (a) 24V, (b) 28V, and (c) 32V;

FIG. 6 shows average thicknesses of Pt and ZnO under various biasvoltages;

FIG. 7 shows average coverage lengths of Pt and ZnO under various biasvoltages;

FIG. 8 presents cross-sectional TEM images of nanodevices afterselective deposition Pt through a given number of deposition cyclesunder various bias voltages (20V, 24V, 28V, and 32V);

FIGS. 9A and 9B are a schematic view and a cross-sectional view of anembodiment of the nano-sensing chip of the invention;

FIGS. 10A and 10B are a schematic view and a cross-sectional view ofanother embodiment of the nano-sensing chip of the invention;

FIG. 11A to FIG. 11I are schematic views of an embodiment of the methodof forming the nanodevice of the invention;

FIG. 12A presents a TEM image of selective deposition 10 nm Pt on thelightly-doped region of a 60 nm thick device channel of the nano sensingdevice;

FIG. 12B shows the detection response of hydrogen (1000 ppm) of the nanosensing device (selective deposition of 10-nm Pt on channel) of FIG. 12Aunder device Joule self-heating;

FIG. 13A presents a TEM image of selective deposition 3 nm Pt on thelightly-doped region of a 10 nm thick device channel of the nano sensingdevice; and

FIG. 13B shows the detection response of hydrogen (1000 ppm) of the nanosensing device of FIG. 13A under device Joule self-heating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a method for forming a nano sensing chip,particularly a method for forming a nano sensing chip by selectivedeposition of sensing materials through device-localized Joule heatingand CVD or ALD, so the method of the invention can be applied to themanufacture of nanodevices or prevent contamination or peeling ofpreviously deposited materials, but not limited thereto. Hereinafter,embodiments of the invention will be described in detail with referenceto the drawings.

As shown in FIG. 1A and FIG. 1B, in an embodiment, the method of forminga nano sensing chip includes forming a nanodevice 10 having a region(such as 101) capable of producing localized Joule heating; and in a CVDsystem or an ALD system enabling the region of the nanodevice 10 producelocalized Joule heating and depositing a sensing material only on theregion (such as 101).

Specifically, as shown in FIG. 1A, the step of forming the nanodevice 10includes forming a device channel 100 having a lightly-doped region 101,and the lightly-doped region 101 is the region capable of producinglocalized Joule heating. The nanodevice 10 further includes a source 110and a drain 120. Two ends of the device channel 100 electricallyconnecting the source 110 and the drain 120. In an embodiment, thedevice channel 100 preferably further includes two heavily-doped regions102. The two heavily-doped regions 102 are disposed at two ends of thelightly-doped region 101 and adjoin the source 110 and the drain 120,respectively. In an embodiment, the device channel 100 includes asemiconductor material, and the device channel 100 can be a nanobelt ora nanowire, but not limited thereto. In another embodiment, the devicechannel 100 can include any semiconductor materials as appropriate.According to practical applications, the doped region can be an n-dopedregion or a p-doped region. In an embodiment, the nanodevice 10 can be an⁺/n⁻/n⁺ doped dual junction nanodevice. For example, the nanodevice caninclude three doped regions: a 2 μm long n⁻ region (e.g. 101) in themiddle and two 5.5 μm long n⁺ regions (e.g. 102) at two distal ends, butnot limited thereto. In another embodiment, the nanodevice 10 can be ap⁺/p⁻/p⁺ doped dual junction poly or single crystalline nanodevice, andthe length of each doped region can be modified according to designneeds. In an embodiment, the lightly-doped region 101 preferably has adoping dosage less than 1×10¹⁴/cm², and the heavily-doped regionpreferably has a doping dosage larger than 1×10¹⁵/cm². Therefore, thepower dissipation at n⁻ region is relatively larger, and the n⁻ regionis capable of producing localized Joule heating. That is, thelightly-doped region 101 is the region capable of producing Jouleheating of the nanodevice 10. For example, n typed dopant preferablyincludes phosphorous or arsenic, and the doping dosage of the n⁻ regionis preferably 8×10¹³/cm², and the doping dosage of the n⁺ region ispreferably 3×10¹⁵/cm². The resistance of the n⁻ region and the n⁺ regionis 30.3 and 6.06 kΩ, respectively, so the power dissipation at the n⁻region is at least 5-fold larger than that at the n⁺ region.

As shown in FIG. 1A, the step of forming the nanodevice includes forminga plurality of the nanodevices. Specifically, the plurality ofnanodevices 10 are formed on a substrate 20 in an array arrangement. Forexample, the substrate 20 is preferably a semiconductor substrate or asemiconductor on insulator substrate, such as silicon substrate orsilicon on insulator substrate. In this embodiment, the plurality ofnanodevices 10 are formed on the substrate 20 having an insulation layer(e.g. oxide layer) 24 stacked on a silicon substrate 22, but not limitedthereto. The plurality of nanodevices 10 are preferably divided inseveral groups according to sensing materials to be deposited thereon,so each group of nanodevice(s) 10 can be independentlyelectrical-biased. For example, the plurality of nanodevices can bedivided into a first group 10A and a second group 10B. Each of the firstgroup 10A and the second group 10B includes at least one nanodevice 10,e.g. five nanodevices in each group in this embodiment, but not limitedthereto. In the same group, the device channels 100 are preferablyconnected to a common source 110 and a common drain 120, so thenanodevices 10 in the same group can be effectively controlled at thesame time. It is noted that each group includes at least one nanodevice,and the number of nanodevices in each group can be the same ordifferent. Moreover, for a same sensing material, the plurality ofnanodevices can be divided into one or more than one group according topractical applications.

As shown in FIG. 1B, the substrate 20 with the nanodevices formedthereon is placed in a CVD system or an ALD system. The nanodevices 10are connected to an external power supply 40 through a printed circuitboard 30 and wires. Specifically, the power supply 40 and the printedcircuit board 30 can control the bias voltage applied to the nanodevice10, so the lightly-doped region 101 of the nanodevice 10 can producelocalized Joule heating, and the sensing material (indicated by dottedlines in FIG. 1A) is deposited on the lightly-doped region 101 of thenanodevice 10. For example, when applying the bias voltage to thenanodevice 10 to enable the lightly-doped region 101 produce localizedJoule heating and increase the temperature of the lightly-doped region101, the reaction gas(es) is introduced through the gas inlet 51, so thesensing material can be deposited only on the lightly-doped region 101of the nanodevice 10 through CVD or ALD, and the residual gas(es) isexhausted through the gas outlet 52. It is noted that the temperature ofthe lightly-doped region 101 can be controlled by controlling the biasvoltage applied to the nanodevice 10 through the power supply 40, andthe thickness of the sensing material deposited on the lightly-dopedregion 101 can be controlled by controlling the number of depositioncycles (or the deposition time) and the bias voltage (the depositiontemperature).

Moreover, when multiple sensing materials are to be deposited on thenanodevices, by controlling the bias voltage applied to individualnanodevices, various sensing materials can be sequentially andselectively deposited on different nanodevices. In an embodiment, thestep of enabling the region produce localized Joule heating includes:enabling the region of the nanodevice in the first group 10A producelocalized Joule heating to deposit the sensing material (e.g. the firstsensing material 210 of FIG. 9A) only on the region of the nanodevice 10in the first group 10A. Specifically, only the nanodevices 10 in thefirst group 10A are electrical-biased through the power supply 40 andthe printed circuit board 30, so the lightly-doped regions 101 of thedevice channels 100 of the nanodevices 10 in the first group 10A producelocalized Joule heating, and the sensing material (e.g. the firstsensing material 210 of FIG. 9A) is deposited only on the lightly-dopedregions 101 of the nanodevices 10 in the first group 10A. For example,when the nanodevices 10 in the first group 10A are electrical-biasedenabling the lightly-doped regions 101 thereof produce localized Jouleheating and increase the temperature of the lightly-doped regions 101,the reaction gas is introduced through the gas inlet 51, and the firstsensing material 210 is deposited only on the lightly-doped regions 101of the nanodevices 10 in the first group 10A through plasmas-enhancedCVD (PECVD) or plasmas-enhanced ALD (PEALD) to achieve selectivedeposition of the first sensing material 210.

The method of the invention further includes: enabling the regions ofthe nanodevices 10 in the second group 10B produce localized Jouleheating to deposit another sensing material (e.g. the second sensingmaterial 220 of FIG. 9A) different from the first sensing material onlyon the regions of the nanodevices in the second group 10B. Thenanodevices 10 in the second group 10B are different from thenanodevices 10 in the first group 10A. For example, after the firstsensing material 210 is deposited, only the nanodevices 10 in the secondgroup 10B are electrical-biased through the power supply 40 and theprinted circuit board 30, so the lightly-doped regions 101 of the devicechannels 100 of the nanodevices 10 in the second group 10B producelocalized Joule heating, and the sensing material (e.g. the secondsensing material 220 of FIG. 9A) is deposited only on the lightly-dopedregions 101 of the nanodevices 10 in the second group 10B. For example,when the nanodevices 10 in the second group 10B are electrical-biasedenabling the lightly-doped regions 101 thereof produce localized Jouleheating and increase the temperature of the lightly-doped regions 101,another reaction gas is introduced through the gas inlet 51, and thesecond sensing material 220 is deposited only on the lightly-dopedregions 101 of the nanodevices 10 in the second group 10B through PECVDor PEALD to achieve selective deposition of the second sensing material220.

In the embodiment, the first sensing material 210 and the second sensingmaterial 220 can be metal materials or metal oxide semiconductormaterials. In an embodiment, the metal material can be selected from thegroup consisting of platinum, palladium, tungsten, and iridium, but notlimited thereto. The metal oxide semiconductor materials can be selectedfrom the group consisting of tin oxide, zinc oxide, tungsten oxide,aluminum oxide, and hafnium oxide, but not limited thereto. Hereinafter,in an embodiment, the method of the invention is illustrated byselectively depositing Pt and ZnO through device-localized Joule heatingand PEALD.

Specifically, when Pt is deposited on the lightly-doped regions 101 ofthe nanodevices 10 in the first group 10A by PEALD, the nanodevices 10in the first group 10A are electrical-biased enabling the lightly-dopedregions 101 thereof produce localized Joule heating. Precursors of Pt(e.g. MeCpPtMe3, Trimethyl-(methylcyclopentadienyl)Platinum) areintroduced into the reaction chamber, and then O₂ plasmas treatment isperformed. Consequently, Pt is selectively deposited only on thelightly-doped regions 101 of the nanodevices 10 in the first group 10A.Next, when ZnO is deposited on the lightly-doped regions 101 of thenanodevices 10 in the second group 10B by PEALD, the nanodevices 10 inthe second group 10B are electrical-biased enabling the lightly-dopedregions 101 thereof produce localized Joule heating. Precursors of ZnO(e.g. diethylzinc, DEZ) are introduced into the reaction chamber, andthen O₂ plasmas treatment is performed. Consequently, ZnO is selectivelydeposited only on the lightly-doped regions 101 of the nanodevices 10 inthe second group 10B. It is noted that the sensing materials can beselected according to practical applications, and the precursors can beselected according to sensing materials, so different sensing materialscan be deposited on different nanodevices in the same chip, not limitedto the embodiments.

FIG. 2 presents AFM and SEM images after ALD (or CVD) for selectivedeposition of Pt and ZnO on the n⁻ region of the device channel forvarious numbers of deposition cycles, (a) 10 cycles, (b) 20 cycles, and(c) 30 cycles. As shown in FIG. 2, under a bias of 20 V and after 10cycles of deposition, both Pt and ZnO nanoclusters are formed on thesurface of the n⁻ region of the device channel. When the number ofdeposition cycles increases to 20 and 30, the aggregation of the Pt andZnO nanoclusters is intensified, and the deposited thickness isincreased.

Moreover, AFM can also be used to characterize the material averagethickness and average coverage in the n⁻ region. As shown in FIG. 3, forPt, the average thickness is 3.85±1.1 nm after 10 cycles, 15.23±1.23 nmafter 20 cycles, and 24.12±1.02 nm after 30 cycles, wherein the growthper cycle (GPC) is 8.04 Å/cycle. For ZnO, the average thickness is4.12±0.83 nm after 10 cycles, 23.12±1.27 nm after 20 cycles, and57.64±0.82 nm after 30 cycles, wherein the GPC is 19.21 Å/cycle. Asshown in FIG. 4, for Pt, the average coverage length is 0.656±0.03 mafter 10 cycles, 0.734±0.02 μm after 20 cycles, and 0.97±0.02 μm after30 cycles. For ZnO, the average coverage length is 0.48±0.03 μm after 10cycles, 0.694±0.02 μm after 20 cycles, and 1.103±0.03 μm after 30cycles. Under substantial identical deposition conditions, thedeposition rate of ZnO is 2.3 times faster than that of Pt, so the sizeof ZnO nanoclusters is greater than that of Pt nanoclusters.

FIG. 5 presents AFM and SEM images after ALD (or CVD) for selectivedeposition of Pt and ZnO through a given number of deposition cycles onthe lightly-doped region of the device channel under various biasvoltages, (a) 24V, (b) 28V, and (c) 32V. As shown in FIG. 5, the givennumber of deposition cycles is 10 cycles. Agglomeration of thenanoclusters becomes evident upon increasing the temperature in the n⁻region. As shown in FIG. 6, for Pt, the average thickness is 5.18±1.01nm at 24V, 11.2±1.01 nm at 28V, and 26.7±1.02 nm at 32V. For ZnO, theaverage thickness is 7.8±1.02 nm at 24V, 18.8±1.02 nm at 28V, and38.8±1.23 nm at 32V at the two sides, as well as 4.4±1.02 nm at themiddle of n⁻ region. As shown in FIG. 7, for Pt, the average coveragelength is 1.09±0.02 μm at 24V, 1.36±0.04 μm at 28V, and 0.88±0.02 μm at32V. For ZnO, the average coverage length is 1.14±0.03 μm at 24V,1.437±0.06 μm at 28V, and 0.9±0.03 μm at 32V. The average coveragesreach their maxima for the selective depositions of both Pt and ZnOunder a bias of 28V. At a bias of 32V, the high device surfacetemperature results in high mobility, such that the average coverage ofPt is lower, but larger nanoclusters are formed in the middle of the n⁻region.

FIG. 8 presents cross-sectional TEM images of nanodevices afterselective deposition through a given number of deposition cycles undervarious bias voltages (20V, 24V, 28V, and 32V). As shown in FIG. 8, thelightly-doped region of the silicon nanodevice is completely covered bya thin Pt layer when the Joule heating power is 24V or 28V, formingtrigate-like structures (e.g. shown in bottom left and upper right). ForJoule heating biases of 20V and 32V, the silicon device channel iscovered by Pt nanoparticles, rather than thin films (e.g. shown in upperleft and bottom right). At low bias and cycle number (e.g. 24V, 10cycles), similar trigate-like surface coverage is shown after theselective deposition of Pt and ZnO.

Furthermore, the method of the invention can be employed forapplications of nano sensing chips, such as nano gas sensing chip, sovarious sensing materials can be deposited on individual nanodevices ina same chip, which can be applied to sensing applications of multipletarget gases. The nano sensing chip can also function under device Jouleself-heating, so as to effectively reduce the sensing power consumption.When the nanodevices are adopted in the nano sensing chip, nanobelts ornanowires can serve as the sensing regions or the device channels of thenanodevices. As shown in FIG. 9A and FIG. 9B, in an embodiment, the nanosensing chip 1 of the invention includes a plurality of nanodevices 10,a first sensing material 210, and a second sensing material 220. Eachnanodevice 10 includes a source 110, a drain 120, and a device channel100 with two ends electrically connecting the source 110 and the drain120. The device channel 100 includes a lightly-doped region 101. Thefirst sensing material 210 is deposited on the lightly-doped regions 101of the nanodevices 10 in the first group 10A. The second sensingmaterial 220 is deposited on the lightly-doped regions 101 of thenanodevices 10 in the second group 10B. The nanodevices 10 in the secondgroup 10B are different from the nanodevices 10 in the first group 10A,and the second sensing material 220 is preferably different from thefirst sensing material 210.

Specifically, the arrangement of the plurality of nanodevices is similarto the arrangement in FIG. 1A. For example, the plurality of nanodevices10 can be divided into several groups according to the sensingmaterials, and each group of nanodevices can be independently operated,so the first sensing material 210 and the second sensing material 220are targeted to different gas molecules. For example, the plurality ofnanodevices 10 are divided into the first group 10A and the second group10B based on the first sensing material 210 and the second sensingmaterial 220, respectively. Each of the first group 10A and the secondgroup 10B includes at least one nanodevice 10 (e.g. five nanodevices).In an embodiment, the device channels 100 of the nanodevices 10 in thefirst group 10A or the second group 10B are parallel to each other, andadjacent device channels 100 are preferably spaced apart by a distanceequal to or larger than 1 μm, but not limited thereto. In a same group,the device channels 100 of nanodevices 10 are preferably connected to acommon source 110 and a common drain 120, so the temperature of thenanodevices in the same group can be effectively controlled at the sametime, but not limited thereto.

Furthermore, the structure of each nanodevice 10 is similar to thestructure in FIG. 1A. For example, the device channel 100 can be an⁻/n⁻/n⁺ or p⁺/p⁻/p⁺ doped dual junction poly or single crystallinedevice channel. The doping dosage of the lightly-doped region ispreferably less than 1×10¹⁴/cm², and the doping dosage of theheavily-doped region is preferably larger than 1×10¹⁵/cm², so the powerdissipation at n⁻ region is relatively larger, and the n⁻ region iscapable of producing localized Joule heating, but not limited thereto.It is noted the details of nanodevice can refer to the relateddescriptions of FIG. 1A and will not be elaborated again.

As shown in FIG. 9B, each nanodevice 10 further includes a dielectriclayer 130. The dielectric layer 130 is disposed between the devicechannel 100 and the first sensing material 210 (or the second sensingmaterial 220). In an embodiment, the dielectric layer 130 can be asingle-layered structure of oxide or nitride (e.g. SiO₂ or Si₃N₄). Inanother embodiment, the dielectric layer 130 can be a dual-layeredstructure including oxide and nitride. For example, a stack of silicondioxide and silicon nitride can be formed on the silicon device channelas the dielectric layer 130.

The first sensing material 210 and the second sensing material 220 canbe selectively deposited through localized Joule heating and PECVD orPEALD as described above. For example, by sequentiallyelectrical-biasing the nanodevices 10 in the first group 10A and thenanodevices 10 in the second group 10B, the first sensing material 210is deposited on the dielectric layer 130 corresponding to thelightly-doped regions 101 of the nanodevices 10 in the first group 10A,and the second sensing material 220 is deposited on the dielectric layer130 corresponding to the lightly-doped regions 101 of the nanodevices 10in the second group 10B. That is, the first sensing material 210 and thesecond sensing material 220 are formed on the dielectric layer 120 andcorrespond to the lightly-doped regions 101 of the nanodevices 10 in thefirst group 10A and the second group 10B, respectively. As describedabove, the first sensing material 210 and the second sensing material220 are independently a metal material or a metal oxide semiconductormaterial. For example, the metal material can be selected from the groupconsisting of platinum, palladium, tungsten, and iridium, and the metaloxide semiconductor material can be selected from the group consistingof tin oxide, zinc oxide, tungsten oxide, aluminum oxide, and hafniumoxide, but not limited thereto. In an embodiment, the first sensingmaterial 210 can be Pt, and the second sensing material 220 can be ZnO,which are configured to detect specific molecules, such as hydrogen andoxygen. It is noted that the sensing material can be selected based onthe target gas and is not limited to the metal materials or the metaloxide materials in the embodiment.

In another embodiment, as shown in FIG. 10 A and FIG. 10B, the nanosensing chip 1′ includes a plurality of suspending nanodevices having agap S between the device channel and the substrate. In an embodiment,the gap S between the device channel 100 and the substrate 20 ispreferably equal to or larger than 7 μm, and adjacent device channels100 are preferably spaced apart by a distance preferably equal to orlarger than 7 μm, so the nanodevices can have a three-dimensionalreaction with the surrounding gases. The suspending nanodevices can beformed by semiconductor manufacturing processes, such as deposition,lithography, etching, ion implantation. Then, the sensing materials areselectively deposited through localized Joule heating and CVD or ALD asdescribed above. In an embodiment, as shown in FIG. 11A, an insulationlayer 24 is formed on a silicon substrate 22, and a semiconductor activelayer 300 is formed on the insulation layer 24. For example, a 7000 nmoxide layer is formed on the silicon wafer, and a 70 nm silicon layer isformed on the oxide layer. As shown in FIG. 11B, the active layer 300 ispatterned to define the nanodevice. For example, the silicon layer ispatterned by the processes, such as lithography, etching, to define thepatterns of source 110, drain 120, and device channel 100. As shown inFIG. 11C, a first implantation is performed to form the lightly-dopedregion 101. Specifically, the first implantation with a dose of3×10¹³/cm² is performed on the source 110, the drain 120, and the devicechannel 100. As shown in FIG. 11D, a second implantation is performed toform heavily-doped regions 102 at two sides of the lightly-doped region101. For example, after the first implantation, photoresist 310 masksthe lightly-doped region 101, and the second implantation with a dose of5×10¹⁵/cm² is performed on the unmasked regions (e.g. source 110, drain120). It is noted that FIG. 11D shows the photoresist 310 partiallymasks the device channel 100 as the lightly-doped region 101; however,in other embodiments, the photoresist 310 can mask the entire devicechannel 100 as the lightly-doped region 101, and the source 110 and thedrain 120 serve as the heavily-doped regions at two sides of thelightly-doped region 101. As shown in FIG. 11E, a dielectric layer 130is formed on the device channel 100. For example, after the secondimplantation, the photoresist 310 is removed, and a 5 nm oxide layer 132and a 10 nm nitride layer 134 are sequentially formed on the devicechannel 100. It is noted that when the step of FIG. 11E is completed,the non-suspending nanodevice (e.g. the nanodevice 10 in FIG. 1A) isformed. The suspending nanodevice can be formed through the steps inFIG. 11F to FIG. 11I.

As shown in FIG. 11F, a passivation layer 320 is formed on thenanodevice. For example, a TEOS (tetraethyl orthosilicate) oxide layeris deposited on the silicon wafer. As shown in FIG. 11G and FIG. 11H,the passivation layer 320 is patterned to define the sensing region(i.e. the channel region). For example, the TEOS oxide layer ispatterned to define the device channel 100. That is, photoresist 330masks the source 110 and the drain 120, and the TEOS oxide layer ispartially removed to expose the device channel 100. As shown in FIG.11I, the insulation layer 24 under the device channel 100 is removed bywet etching to form the gap S under the device channel 100. For example,the oxide layer under the device channel 100 is removed in wet etchingsolution (such as HF solution) to form the gap S between the devicechannel 100 and the silicon substrate 22 (or the residual oxide layer),and therefore the suspending nanodevice is formed. Then, various sensingmaterials are selectively deposited on the lightly-doped regions 101 ofthe device channels 100 of different nano devices through localizedJoule heating and CVD or ALD as described above, so the nano sensingchip with suspending nanodevices shown in FIG. 10A and FIG. 10B isformed.

FIG. 12A presents a TEM image of selective deposition 10 nm Pt on then-region of a 60 nm thick device channel of the nano sensing device.FIG. 12B shows the detection response of hydrogen (1000 ppm) of the nanosensing device of FIG. 12A under device Joule self-heating. As shown inFIG. 12A and FIG. 12B, for the nano sensing device having a devicechannel thickness of 60 nm, even though the nano sensing device isfunctioned under device Joule self-heating, 15V is required to obtainabout 2.1% hydrogen response, and the power consumption for gasdetection is about 16 nW. FIG. 13A presents a TEM image of selectivedeposition 3 nm Pt on the n-region of a 10 nm thick device channel ofthe nano sensing device. FIG. 13B shows the detection response ofhydrogen (1000 ppm) of the nano sensing device of FIG. 13A under deviceJoule self-heating. As shown in FIG. 13A and FIG. 13B, for the nanosensing device having a device channel thickness of 10 nm, the nanosensing device is functioned under device Joule self-heating, merely 1Vis required to obtain about 97% hydrogen response. Furthermore, as thevolume of the n⁻ region is reduced from 0.5 μm(W)×2 μm(L)×60 nm(T) inFIG. 12A to 0.35 μm(W)×1 μm(L)×10 nm(T) in FIG. 13A, the sensing voltageunder device Joule self-heating is reduced from 15 V to 1V, and thesensing power consumption is also reduced from about 16 nW to about 1nW.

In other words, the thickness of the device channel will greatly affectthe sensitivity and the sensing power consumption. In an embodiment, thethickness of the device channel is preferably less than the Debye lengthto reduce the sensing power consumption under device Joule self-heating.The Debye length is a measure of a charge carrier's net electrostaticeffect and how far its electrostatic effect persists (i.e. chargescreening characteristics). For example, when the nanodevice is an+/n−/n+ doped dual junction poly or single crystalline nanodevice, thedevice channel can be a nanobelt or a nanowire, and the thickness of thenanobelt or the diameter of the nanowire is preferably less than 20 nm.

Compared to the prior art, the invention provides a method for selectivedeposition of metal and/or metal oxide semiconductor on thelightly-doped regions of nanodevices through localized Joule heating andCVD or ALD, which is superior in applications of manufacturingnanodevices. Moreover, the method of the invention utilizes localizedJoule heating and CVD or ALD to sequentially selectively deposit varioussensing materials on specific regions by controlling the bias voltage ofthe specific regions, simplifying the manufacturing process withoutcontaminating or damaging the previously deposited sensing materials.Moreover, invention selectively deposits different materials on specificregions of individual nanodevices, and the specific regions are highlysensitive in response to changes in surface potential. For gas-sensingapplications, individual nanodevices can be functioned under deviceJoule self-heating to increase the surface temperature of the specificregions to optimize the reaction temperature (e.g. different reactiontemperatures for different sensing materials and target gases), so as toachieve optimum gas detections. The nano sensing devices which functionunder device Joule self-heating can reduce the power consumption, whichis generally greater than 25 mW/device for conventional gas sensingdevice. The nano sensing chip of the invention can be applied to sensingapplications of multiple gases under device Joule self-heating toimprove the device sensitivity and the device portability, suitable forambient gas monitoring or gas sensing in human exhaled breath fordisease diagnosis.

Although the preferred embodiments of present invention have beendescribed herein, the above description is merely illustrative. Thepreferred embodiments disclosed will not limit the scope of the presentinvention. Further modification of the invention herein disclosed willoccur to those skilled in the respective arts and all such modificationsare deemed to be within the scope of the invention as defined by theappended claims.

What is claimed is:
 1. A method for forming a nano sensing chip,comprising of a step: forming a nanodevice comprising a source, a drain,and a device channel with two ends capable of being biased, the devicechannel having a lightly-doped region capable of producing localizedJoule heating; and in a chemical vapor deposition (CVD) system or anatomic layer deposition (ALD) system electrical-biasing the nanodeviceso that the localized Joule heating modulates temperature of thelightly-doped region of the nanodevice enabling a selective depositionof a sensing material only on the lightly-doped region.
 2. The method ofclaim 1, wherein the step of forming the nanodevice includes forming aplurality of nanodevices, and the step of enabling the selectivedeposition includes electrical-biasing the plurality of nanodevices in afirst group so that the localized Joule heating modulates thetemperature of the lightly-doped regions of the plurality of nanodevicesin the first group enabling the selective deposition of the sensingmaterial only on the lightly-doped regions of the plurality ofnanodevices in the first group.
 3. The method of claim 2, after theselective deposition of the sensing material on the lightly-doped regionof the plurality of nanodevices in the first group is performed, furthercomprising: electrical-biasing the plurality of nanodevices in a secondgroup so that the localized Joule heating modulates the temperature ofthe lightly-doped regions of the plurality of nanodevices in the secondgroup enabling a selective deposition of another sensing materialdifferent from the sensing material only on the lightly-doped region ofthe plurality of nanodevices in the second group, wherein the devicechannels of the plurality of nanodevices in the first group areconnected to a first common source and a first common drain, and thedevice channels of the plurality of nanodevices in the second group areconnected to a second common source and a second common drain differentfrom the first common source and the first common drain.
 4. The methodof claim 1, wherein the step of forming the nanodevice includes formingthe device channel having the lightly-doped region between twoheavily-doped regions.
 5. The method of claim 1, wherein the sensingmaterial is selected from the group consisting of platinum, palladium,tungsten, iridium, tin oxide, zinc oxide, tungsten oxide, aluminumoxide, and hafnium oxide.
 6. The method of claim 1, further comprisingforming a dielectric layer on the device channel, and the sensingmaterial is deposited on the lightly-doped region with the dielectriclayer interposed therebetween.
 7. A method for forming a nano sensingchip, comprising: forming a plurality of nanodevices into a first groupand a second group, each of the first group and the second groupcomprising one or more of the plurality of nanodevices, each of one ormore of the plurality of nanodevices comprising a source, a drain, and adevice channel with two ends capable of being biased, the channel devicehaving a lightly-doped region capable of producing localized Jouleheating; in a CVD system or an ALD system electrical-biasing the one ormore of the plurality of nanodevices in the first group so that thelocalized Joule heating modulates temperature of the one or morelightly-doped regions of the one or more of the plurality of nanodevicesin the first group enabling a selective deposition of a first sensingmaterial only on the one or more lightly-doped regions of the one ormore of the plurality of nanodevices in the first group; and after thefirst sensing material is deposited, electrical-biasing the one or moreof the plurality of nanodevices in the second group so that thelocalized Joule heating modulates temperature of the one or morelightly-doped regions of the one or more of the plurality of nanodevicesin the second group enabling a selective deposition of a second sensingmaterial only on the one or more lightly-doped regions of the one ormore of the plurality of nanodevices in the second group.
 8. The methodof claim 7, wherein the step of forming the plurality of nanodevicesincludes forming an array of the plurality of nanodevices, each of thedevice channels comprises the lightly-doped region between twoheavily-doped regions.
 9. The method of claim 7, wherein the firstsensing material and the second sensing material are independently ametal material or a metal oxide semiconductor material.
 10. The methodof claim 9, wherein the metal material is selected from the groupconsisting of platinum, palladium, tungsten, and iridium, and whereinthe metal oxide semiconductor material is selected from the groupconsisting of tin oxide, zinc oxide, tungsten oxide, aluminum oxide, andhafnium oxide.
 11. The method of claim 7, wherein the device channels ofthe plurality of nanodevices in the first group are connected to a firstcommon source and a first common drain, and the device channel of theone or more of the plurality of nanodevices in the second group areconnected to a second common source and a second common drain differentfrom the first common source and the first common drain.
 12. The methodof claim 7, wherein the first sensing material is different from thesecond sensing material, and the step of electrical-biasing the one ormore of the plurality of nanodevices in the first group and the step ofelectrical-biasing the one or more of the plurality of nanodevices inthe second group are performed by applying different bias voltages tothe one or more of the plurality of nanodevices in the first group andin the second group.
 13. The method of claim 7, wherein the firstsensing material is different from the second sensing material, and theone or more of the plurality of nanodevices in the first group and thesecond group are configured to function under Joule self-heating atdifferent working temperatures to simultaneously sense different targetgases by the first sensing material and the second sensing material,respectively.
 14. The method of claim 7, further comprising forming adielectric layer on the device channel of the one or more of theplurality of nanodevices, and the first sensing material or the secondsensing material is deposited on the one or more lightly-doped regionsof the one or more of the plurality nanodevices in the first group orthe second group with the dielectric layer interposed therebetween.